Storage batteries are commonly used in emergency power systems and power driven transporters because of their portability and relatively small size. However, to serve longer term loading requirements and enlarge battery capacities, an increase in cost and overall weight is inevitably incurred, and in addition, the serviceable life of the battery is decreased by exposure to discharging under heavy load conditions. The subject invention addresses these problems by providing auxiliary charging where needed to stationary or vehicle-carried batteries so as to keep them in adequately charged condition at all times and ready for all eventualities.